dental plaque Biofilm Dr Alaa

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Information about dental plaque Biofilm Dr Alaa

Published on December 17, 2012

Author: draatia


PowerPoint Presentation: صدق الله العظيم ،، س ــــ ورة البق ــ رة آيه (32) PowerPoint Presentation: Dental Plaque Biofilm Associate Professor Dr Alaa M Attia PowerPoint Presentation: A biofilm is a well-organized community of bacteria that adheres to surfaces and is embedded in an extracellular slime layer. It Contain more than 400 species of bacteria It’s a heterogeneous in structure Dental Plaque biofilm PowerPoint Presentation: Dental plaque is seen on cervical portion of tooth structure PowerPoint Presentation: Dental plaque is detected by disclosing agent PowerPoint Presentation: Calculus and plaque deposits PowerPoint Presentation: 1- Bacterial micro-colonies (15 – 20 % by volume) distributed in shaped matrix or glycocalyx (80 – 85 %). 2- Extracellular matrix represent backbone of matrix: - maintain the integrity of biofillm - Act as a buffer and a substrate for resident bacteria - protection for microorganisms & resist the antibacterial subs. 3- Presence of voids or water channels - permit the passage of nutrients and other agents, acting as – circulatory system Structure of Biofilm PowerPoint Presentation: Plaque Biofilm PowerPoint Presentation: Intermicrobial Matrix of plaque biofilm Organic component Inorganic component PowerPoint Presentation: Organic constituents : - polysaccharides - proteins - glycoproteins and lipids. Glycoproteins : from saliva are an important component of the pellicle that initially coats a clean tooth surface which later become incorporated into the developing plaque biofilm . Polysaccharides: produced by bacteria (such as dextran ) serve as energy storage or as anchorage material to secure their retention in plaque. - Lipid : material in the organic content is derived from the membranes of disrupted bacterial and host cells and food debris. PowerPoint Presentation: Inorganic component: - M ainly calcium and phosphorus with trace amounts of other materials such as sodium, potassium and fluoride The source of inorganic constituents of supragingival plaque is mainly saliva . Inorganic component of subgingival plaque is derived from the crevicular fluid which is a serum transudate . PowerPoint Presentation: Tooth deposits Dental plaque: It’s a resilient yellow-grayish substance that adheres tenaciously to the intraoral hard surfaces, including removable and fixed restorations. Materia alba : It’s a soft accumulations of bacteria and tissue cells that lack the organized structure of dental plaque and are easily displaced with a water spray . (mainly desquamated epithelial cells & food debris). Calculus : It’s a hard deposit that forms by mineralization of dental plaque and is generally covered by a layer of unmineralized plaque . PowerPoint Presentation: Types of dental plaque biofilm 1- Supragingival plaque: (mainly Gram + ve bacteria, aerobic) 2- Subgingival plaque: (mainly Gram - ve bacteria, anerobic ) - Tooth associated - Epithelial associated - Unattached plaque PowerPoint Presentation: Plaque – bacteria association with tooth surface and periodontal tissues PowerPoint Presentation: Accumulation of a dental plaque biofilm PowerPoint Presentation: Accumulation of a dental plaque biofilm 1- Formation of the pellicle 2-Initial adhesion/attachment of bacteria 3- Colonization / Plaque maturation PowerPoint Presentation: 1- F ormation of dental pellicle . Its a glycoprotein which derived from components of saliva and GCF as well as bacterial and host tissue cell products and debris . (2 layer basal (difficult removed) &thicker globular layer (easily removed) Mechanism of pellicle adsorption to tooth surface: 1- Electrostatic force. 2- Van der Waal. 3- Hydrophobic forces. Function of pellicle: 1- Protective barrier 2- Lubrication 3- Substrate to the bacterial attachment PowerPoint Presentation: 2- Initial attachment of bacteria - Tooth brush remove most of bacteria but not all from tooth surface - bacteria can be detected within 3 minutes of introducing sterile enamel into the mouth. The attachment of bacteria need - bacterial adhesins - tissue receptors Tooth surface, tissues receptor bacteria Adhesin PowerPoint Presentation: The initial colonizers species to dental pellicle are: - Streptococcus sp. - Haemophilus sp. - Neisseria sp. - Actinomyces sp. - Veillnella sp. Primary colonizers produce low oxygen tension that permit the survival and growth of obligate anaerobes. Obligate aerobes Facultative PowerPoint Presentation: Initial attachment of bacteria include 3 phases a- Transport to the surface b- Initial adhesion c- Strong attachment PowerPoint Presentation: a- Transport to the surface By the following 1- Brownian motion (average displacement of 40 um/hour). 3- Sedimentation of microorganisms. 3- Liquid flow 4- Active bacterial movement ( chemotactic activity) 5- Mechanical contact between oral soft tissues and teeth. The above techniques are bringing the primary colonizing bacteria into contact with teeth. PowerPoint Presentation: b- Initial adhesion its reversible adhesion of the bacterium to be closely to the surface (separation distance 50 nm). Forces of adhesion: through distance by - Van der waals attractive forces - Electrostatic repulsive forces By the above forces the distances closer to 10 nm . PowerPoint Presentation: c- Strong attachment its irreversible attachment The binding between bacteria and pellicle is mediated by specific adhesins on the bacterial cell surface (usually proteins) . e.g. - fimbirae - surface protein - antigen I/II family adhesin Receptors (proteins – glycoproteins – or polysaccharides) on acquired pellicle PowerPoint Presentation: Many receptors for streptococci include - α - amylase - Acid proline -rich proteins - Stathern - Salivary agglutinin glycoprotein gp340. PowerPoint Presentation: 3- Colonization and plaque maturation: Primary colonizing bacteria provide new receptors to attachment of other bacteria (secondary colonizing bacteria) This mechanism called Coadhesion PowerPoint Presentation: Primary colonizers Streptococus gordonii - Streptococus oralis Streptococus intermedius Streptococus mitis - Streptococus sanguinis Actinomyces gerencseria – Actinomyces oris Actinomyces israelli - Actinomyces odontolyticus Aggregatibacter actinomycetemcomitans sero . A Capnocytophiga gingivalis Capnocytophiga ochracea Capnocytophiga sputigena Eikenella corrodens - Veillonella parvula PowerPoint Presentation: Secondary colonizers Aggregatibacter actinomycetemcomitans sero . B Campylobacter gracilis – Campylobacter rectus Campylobacter showae - Eubacterium nodatum Fusobacterium nucleatum ssp. Fusobacterium periodonticum Prevotella intermidia – Prevotella loescheii Prevotella nigrescens - Tannerella forsythia Porphyromonas gingivalis - Parvimonas micra Streptococcus constellatous Treponema denticola PowerPoint Presentation: Bacterial Co aggregation: Its the ability of different species of plaque to adhere to one another. Co aggregation interactions between gram+ve and gram- ve An example of coagregation : Fusobacterium nucleatum with Streptococcus sanguis Porphyromonas loescheii with Actinomyces viscosus . Capnocytophaga ochracea with Actinomyces viscous . In later stages of plaque formation, co aggregation between different gram-negative species takes place . For example Fusobacterium nucleatum with Porphyromonas gingivalis . PowerPoint Presentation: The microbiology of the forming dental plaque has been investigated in humans (Experimental gingivitis in man, Loe et al. 1965). The oral hygiene of a group of dental students was improved by thorough prophylaxis and meticulous plaque control. This resulted in an excellent gingival condition with almost no plaque. All oral hygiene measures were then withdrawn allowing plaque to reaccumulate along the gingival margin for almost three weeks. PowerPoint Presentation: Primary colonization by predominantly Gram-positive facultative bacteria. Streptococcus sanguis is most dominant. Actinomyces species are also found in 24 h plaque . Gram-positive facultative cocci and rods co aggregate and multiply. Surface receptors on the Gram-positive facultative cocci and rods allow the subsequent adherence of Gram-negative organisms, which have a poor ability to directly adhere to the pellicle. e.g. fusobacterium nucleatum and prevotella intermedia . Plaque ages and matures. As a result of ecologic changes, more Gram-negative strictly anaerobic bacteria colonize secondarily and contribute to an increased pathogenicity of the biofilm . PowerPoint Presentation: After 2-3 weeks, all subjects clinically manifested gingivitis. During this period, plaque samples were collected to study the changes in the flora of the dental plaque. Plaque samples taken before oral hygiene was stopped i.e. healthy gingiva showed few bacteria on the cervical part of the teeth. Most of the bacteria were gram positive cocci and rods ( S. mitis and small amounts of S. sangius and S. mutans ), few actinomyces ( A. viscosus , A. naeslundii ). At that stage, the bacteria are loosely attached to the tooth, but later become firmly attached . During the first phase of plaque development, (first 2 days of experiment) the number of bacteria and the percentage of Gram – ve cocci ( Veillonella ) increased , and together with the Gram – ve rods constituted about 25% of the plaque flora. PowerPoint Presentation: During the second phase of plaque development (3rd and 4th days of experiment) proliferation of fusobacteria and filamentous bacteria starts. During the third phase (5-9 days of the experiment) spirilla and spirochetes appear so that the complex picture seen in old plaque became established. The structure of the mature plaque is a reflection of the stages of development. Supragingivally and close to the tooth surface is a layer of gram-positive cocci (the initial colonizers). PowerPoint Presentation: Towards the surface, the plaque becomes progressively more filamentous and complex. The outer most layer appears to consists mainly of filamentous organisms arranged at right angle to the tooth surface interspersed with many of the coccal gram – ve and gram + ve forms producing a structure with the appearance of “Corn cob”. This is mainly due to interspecies adhesion. As the dentogingival plaque layer increases in thickness, the environment changes to favor anaerobic microorganisms and an increasing number of gram – ve rods grow especially in the deeper layers next to the tooth. These changes in bacterial flora are accompanied clinically be gingivitis with all its inflammatory changes PowerPoint Presentation: This scanning electron micrograph at higher power shows cocci attached to filamentous organisms to produce the corn-cob type of arrangement sometimes seen in plaque PowerPoint Presentation: SEM of mature human dental plaque demonstrating corn cob formation PowerPoint Presentation: Subgingival plaque : Subgingival environment differs from the supragingival environment in several aspects: The gingival crevice has a continuous flow of crevicular fluid which contains substances which bacteria can use as nutrients. The host inflammatory cells and mediators may influence the establishment and growth of the bacteria in the crevice or pocket region. Microbiologic studies of subgingival plaque demonstrated a difference between “tooth associated plaque” and “tissue associated plaque”. PowerPoint Presentation: Color-coded complexes of common subgingival microorganisms according to DNA-hybridization methodology PowerPoint Presentation: Plaque growth curve = Cocci = Bacilli = Motile PowerPoint Presentation: Factors Affecting on supragingival dental plaque formation PowerPoint Presentation: Factors Affecting on supragingival dental plaque formation ============= 1- Topography of supragingival plaque: Initial growth along the gingival margin and from the interdental space (areas protected against shear forces). Later, a further extension in the coronal direction can be observed. Plaque formation can also start from grooves, cracks, perikymata (invisible groves), or pits. PowerPoint Presentation: Growth of plaque along the gingival margins and interdental spaces PowerPoint Presentation: Crack on central upper incisor, several small pits on canine induce gingival plaque accumulation PowerPoint Presentation: 2- Surface microroughness : Smoothing an intraoral surface decreases the rate of plaque formation. Below a certain surface roughness (R a < 0.2 µm). Surface free energy and surface roughness are two factors influencing plaque growth. PowerPoint Presentation: 3- Individual variables influencing plaque formation: The rate of plaque formation differs significantly between subjects, differences that might overrule surface characteristics. A distinction is often made between “heavy” (fast) and “light” (slow) plaque formers. Rapid plaque formers demonstrated higher proportions of gram-negative rods (35% versus 17%) in 14-day-old plaque. PowerPoint Presentation: 4- Variation within the dentition: In general, early plaque formation occurs faster: in the lower jaw (when compared to the upper jaw); in molar areas; on the buccal tooth surfaces, when compared to palatal sites (especially in the upper jaw); and in the interdental regions when compared to the buccal or lingual surfaces. PowerPoint Presentation: 4- Variation on the dentition: In general, early plaque formation occurs faster: in the lower jaw (when compared to the upper jaw); in molar areas; on the buccal tooth surfaces, when compared to palatal sites (especially in the upper jaw); and in the interdental regions when compared to the buccal or lingual surfaces PowerPoint Presentation: 5- Impact of gingival inflammation and saliva: Several studies clearly indicate that early in vivo plaque formation is more rapid on tooth surfaces facing inflamed gingival margins than on those adjacent to healthy gingivae . These studies suggest that the increase in crevicular fluid production enhances plaque formation. Probably, some substance(s) from this exudate (e.g., minerals, proteins, or carbohydrates) favor both the initial adhesion and/or the growth of the early colonizing bacteria. PowerPoint Presentation: During the night, plaque growth rate is reduced by some 50%. This seems surprising, since one would expect that reduced plaque removal and the decreased salivary flow at night would enhance plaque growth. The fact that the supragingival plaque obtains its nutrients mainly from the saliva appears to be of greater significance than the antibacterial activity of saliva PowerPoint Presentation: 6- The impact of Patient′s age: More recent studies clearly indicate that a subject's age does not influence on plaque formation Severe gingival inflammation, which seems to indicate an increased susceptibility to gingivitis with aging. PowerPoint Presentation: 7- Spontaneous tooth cleaning: Some plaque is removed spontaneously from the teeth such as during eating. Even in the occlusal surfaces of the molars, plaque remains, even after chewing fibrous food (carrots, apples, or chips). PowerPoint Presentation: Taken before and after dinner, starting from 4 days of undisturbed plaque formation. Only negligible differences in plaque extent could be observed. PowerPoint Presentation: Microbiologic specificity of periodontal diseases PowerPoint Presentation: Microbiologic specificity of periodontal diseases ===================== 1- Non -specific plaque hypothesis : Its considered that the result from an accumulation of plaque over time, eventually in conjunction with a diminished host response and increased host susceptibility with age. Destruction of periodontal tissues due to total amount of plaque and their noxious products and not specific microorganisms . PowerPoint Presentation: Several observations contradicted these conclusions. First, some individuals with considerable amounts of plaque and calculus, as well as gingivitis, never developed destructive periodontitis . Second Some sites were unaffected, whereas advanced disease was found in adjacent sites. In the presence of a uniform host response, these findings were inconsistent with the concept that all plaque was equally pathogenic. PowerPoint Presentation: 2- Specific plaque hypothesis: The specific plaque hypothesis states that only certain plaque is pathogenic, and its pathogenicity depends on the presence of or increase in specific microorganisms . The specific plaque hypothesis was encouraged by the suggestion that Actinobacillus actinomycetumcomitans was almost always recognized as a pathogen in localized aggressive periodontitis . PowerPoint Presentation: 3- Ecologic Plaque Hypothesis: According to the ecologic plaque hypothesis, both the total amount of dental plaque and the specific microbial composition of plaque may contribute to the transition from health to disease. Accumulation of plaque causes inflammation of adjacent tissues (gingivitis) that affected by environmental changes that favor the growth of gram-negative anaerobes and proteolytic species, including periodontopathogens . PowerPoint Presentation: Metabolism of Dental Plaque Bacteria PowerPoint Presentation: Metabolic interactions among different plaque bacterial species. Streptococcus Actinomyces Streptococcus mutans lactate Formate Protoheme Capnocytophiga Veillonella Fusobacterium Campylobacter Trepanoma Porphyromonas g. & P. intermedia P- Amino benzoate Succinate Isobutryrate Hemin Globin PowerPoint Presentation: Metabolism of Dental Plaque Bacteria - The early colonizers (e.g., streptococci and actinomyces ) utilize the oxygen and lower the reduction-oxidation potential of the environment which then favors the growth of anaerobic species. Gram-positive species use sugars as an energy source and saliva as a carbon source. The bacteria that predominate in subgingival plaque are anaerobic, asaccharolytic , and use amino acids and small peptides as energy sources. PowerPoint Presentation: Studies have demonstrated physiologic interactions among the different bacteria found in dental plaque. Lactate and formate are byproducts of the metabolism of streptococci and actinomyces and may be utilized in the metabolism of other plaque microorganisms. Growth of Porphyromonas gingivalis is enhanced by metabolic by-products produced by other microorganisms such as succinate from capnocytophaga ochracea . PowerPoint Presentation: The host also functions as an important source of nutrients. An example is the bacterial enzymes that degrade the host proteins resulting in the release of ammonia which is used as a nitrogen source for bacteria. Hemin iron which results from breakdown of host hemoglobin is important in metabolism of Porphyromonas gingivalis . Increase in steroid hormones is associated with a significant increase in the proportions of Prevotella intermedia . PowerPoint Presentation: Biofilms and Antimicrobial Resistance PowerPoint Presentation: Biofilms and Antimicrobial Resistance ======================== The resistance of bacteria to antimicrobial agents is dramatically increased in the biofilm . Almost without exception, organisms in a biofilm are 1000 to 1500 times more resistant to antibiotics than in their planktonic or unattached state. PowerPoint Presentation: The resistance of bacteria to antibiotics is affected by: - nutritional status - growth rate - temperature - pH - prior exposure to subeffective concentrations of antimicrobial agents. PowerPoint Presentation: Extracellular enzymes such as β- lactamases , formaldehyde lyase , and formaldehyde dehydrogenase may become trapped and concentrated in the extracellular matrix , thus inactivating some antibiotics (especially positively charged hydrophilic antibiotics ). Some antibiotics , such as the macrolides , which are positively charged but hydrophobic , are unaffected by this process. Antibiotic resistance may be spread through a biofilm by intercellular exchange of DNA . THANK YOU: THANK YOU

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